Biotin intermediate



Patented Jan. 25, 1949 STATES QFFICE 2,460,226 310mm I'NTERMEDIAEIIE Stanton A. Harris, Westfield and. Glen E, Anth,

Ha lw y, N- J ass i o M k & Inc Rahway N. J., a corporation of New Jerseyo D awi e- Ani n Dcnemher .511945, SerialNo. 635,428;

12 Glaims. (Cl. MiG-+329) It is now found that this compound can be synthesized by reactions indicatedas follows:

NH: $31: (in-com GIL-C on! K033343531 I Chg-SH E S-" QEQ 093 1 no ox B5 Q I l NR 7 ROE H-C 02R 1 Hr -002R GH'r-S-CHICOZR om-s-omoo=n (4) (3).- I ROM no 0 no 0 NH 0 NH 0 I II I II GH-C 11+, H 0- cn -w-o I I heat I I CHT-S(|1Q 02R (la s -cm o=cmcnmo 0m no 0 no 0 NH N Y NH 0 I II E- 1 I II r -s Y on,s-c=ou 011030021: CHa-SC=CH 011, 30 02R l (RQQhO In the above formulae, R represents an alkyl, aryl orazflalkylgroup; X, a. halogen; Y-N== a radical selected from the group which consists: of-

, boxymethyl-mercapto-propanoic acid (2); which is then treated with an acylating agent, such as an acyl halide, in an aqueous alkaline solution to yield '2 acylamido-3-carboxymethylmercaptopropahoicijacid (3). This product is esterified I using a mineral acid catalyst to produce the diester (4) of the acid (3), and the diester is treated I with alkali metal alcoholate or an alkaline earth I metal alcoholate to yield the 2-alkali metal or (shed-alkaline. earth metal derivative ofs anl ester of. 2:- carboxy 3 keto 4=w acylar'nido tetra? hyd iebli e (5!)! I, so 7 ea 1 with): d ate wheeleeidyislwdmlnes pxyliated. to. produce 3rketpri-aqylean o-tetrahjrdrothiophene(o) which, when re- This. compound. when acted with 4-carboxy butanal ester in a lower aliphatic alcohol reaction medium containing piperidine and a lower aliphatic carboxylic acid, produces an ester of 2-(4'-carboxybutyl idene)- 3 keto 4 acylamido tetrahydrothiophene (7). This product, when reacted with a compound of the class which consists of hydroxylamine, arylhydrazines, semicarbazide, and salts thereof, yields an ester of the corresponding 3- nitrogen substitution product of 2-(4-carboxybutylidene) 3 keto 4 acylamido-tetrahydrothiophene (8) which upon treatment with a mixture of zinc, a lower aliphatic acid and a lower aliphatic acid anhydride, produces a mixture of 2 (4' carboxy butylidene) 3:4 di(acylamido)-tetrahydrothiophene ester (9a) and 2- (4 carboxybutyl) 3:4 di(acylamido) 4:5- dihydrothiophene ester (9b). This mixture, or

if preferred, one of the components, is then treated with hydrogen in the presence of a hydrogenation catalyst to yield 2-(4'-carboxy-butyl)-3:4- di(acylamido) tetrahydrothiophene ester (10). When this last mentioned compound is treated with an aqueous alkaline solution, hydrolysis of the acyl groups occurs, yielding upon acidification, 2- (4'-carboxy-butyl)'-3 :4-'diamino-tetrahydrothiophene (11) which, when reacted with a carbonyl halide, produces the compound 2-(4- carboxy butyl) 3:4 ureido tetrahydrothiophene. This product is obtained as a mixture of stereoisomers, one of which is racemic biotin, from which upon resolution, is obtained the dextrorotatory isomer, biotin.

This invention is concerned with the intermediates numbered 9a and 9b above, namely 2- (4' carboxy butylidene) 3:4 di(acylamido) tetrahydrothiophenes and their isomers, 2-(4'- carboxy butyl) 3:4 d i(acylamido) 4:5 dihydrothiophene, together with esters of each of the isomers represented by the formulae:

RNl'I a'ien HCII m-s-donrompo 0,11"

and

RNH

H-- I g om-s- (0H,)400zR" wherein R and R. are acyl groups and R" is of the class consisting of hydrogen, aryl, alkyl and arylalkyl.

(4 carboxy butylidene) 3 keto 4 acylamido-tetrahydrothiophene', with an acylatingreducing agent such as a mixture of zinc, a lower aliphatic acid and a lower aliphatic acid anhydride whereby the substituent in the 3-position is simultaneously reduced by nascent hydrogen resulting from interaction of the zinc and the acid, and acylated by the acid anhydride. The corresponding acids are obtained from the esters by saponification followed by treatment with an acid.

The starting materials, used in practicing the process according to this invention, namely the oximes, arylhydrazones and semicarbazones of 2- *(4 carboxy butylidene) 3 keto 4 acyl- ,amido-tetrahydrothiophene esters, can be ob- One of these isomers can be converted operations indicated above and described in copending applications Serial Nos. 554,456 and 554,-

457 both filed September 16, 1944 and Serial No.

635,426 filed December 15, 1945, into the vitamin biotin.

Inasmuch as the 4-acylamido substituent otthe starting material used in practicing the process according to this invention remains unaffected by the process wherein the products according to the invention are obtained, it is evident that usual simple 4-acylamido substituted compounds of that type can be used, for example the following can be employed in the present process:

2 (4' carboxy-butylidene) 3 (p nitro- Q1112 (4' carboxy butylidene) 3 (p nitrophenylhydrazino) 4 propionamido tetrahydrothiophene esters.

Likewise variation in the ester group does not afiect materially the course of the reaction; methyl, ethyl, propyl, butyl, or other lower alkyl,

and phenyl, benzyl and other aryl and arylalkyl esters can beused satisfactorily.

The following examples illustrate methods of carrying out the present invention, but it is to be understood that these examples: are given by way of illustration and not of limitation.

/ (CHaCOhO CcHaCO CHaCO CH5OO CHaCO Nn NH NH NH I I I I CH CH CH C According to the present invention, compounds of the above formulae are obtained as a mixture of the isomers by treating an ester of. a compound of the class which consists of oximes, arylhydrazones and semicarbazones of the ketone, '2

About 10 g. of zinc dust is slowly added, with agitation to a cold mixture of 50 cc. of acetic anhydride, 50 cc. of glacial acetic a id, and about o1 is mtinued ior about 16 hours thereafter. the temperature of the reaction mixture being pemiitted to rise {gradually to about room temperature. Zmc particles in the mixture are then removed; and the solution is evaporated under diminished pressure to obtain a 'wlfite residue. This residue is suspended .in water, warmed to about L51) (3. to decompose any remaining acetic anhydride, cooled and acidified to congo with hydrochloric acid resulting in the precipitation ef crud-e 2-bit -carbomethoxy-butylidene) -3- aeet'amido *Q benzamido-tetrahydrothiophene (9a) together with its corresponding isomer; 2- (4' warbometheXY-butyli--3-acetamido- 4-benzamido-4 :S-dihydrothiophene (Qb') This crude product is removed and purified by known methods.

The crude mixture obtained as a product above comprises a mixture of two stereoisomeric racemates, which when fractionally crystallized from methanol yields a first racemic mixture (M. P. 185-186" C.) corresponding to formula (9b') above, and a relatively more soluble second racemic mixture (M. P. 162-163 C.) corresponding to formula (911) above.

By saponifying 2-(4'-carbomethoxy-buty1- idene) -3- acetamido -4- benzamido-tetrahydrothiophene or its isomer with warm alkali in aqueous alcohol, followed by acidification of the mixture, the corresponding acid, 2-(4-cjarboxy- CHaCOOH (cmcom 1 Zn ctmco craco clmco cmco NE NH 7 N NH (3H (3H E.aS-(B:CH(CH2):COOCH3 About 140 gms. of zinc dust is addedfto a mixture containing about 200 cc. glacial acetic acid and'200 cc. acetic anhydride and this mixture is cooled'to approximately 5 C. About gms. of 2- (4'- carbomethoxy-butylidene) 3 (p-nitrophenyl hydrazlno)- 4- benzamido tetrahydrothiophene is added portionwise ove lija" 10 minute period with good agitation; at the same time maintaining a temperature of appro mately 5 C. Following the addition, the stirring s continued for about 7 hours at 2 0., the zinc dust is filtered off and the solutionallowedto stand overnight at about 0 C. The following day-the solution is evaporated to dryness under reduced ressure and the dry product dissolved in wate decompose residual acetic anhydride. The resulting aqueous solution is extracted three times wit chloroform,

the chloroform extract is washed ith a small amount of water, dried over sodium sulfate and concentrated to small volume. Th small amount of solid present, which'is by-prod diactyhpphenylene-diamine, is removed I; filtration. A small amount of alcohol and etli'e is then added 5 to the clear :chlorcfomn eoncentr ate the solution stirred until a crystalline precipitate forms. This precipitate :is filtered and recrystallized iron: ethanol to produce pure 2- (4-carbcnrethoxywhere R1 and R2 are acyl radicals, and R3 is a radical selected from the group which consists of hydrogen, alkyl radicals, a-ryl radicals and aralkyl radicals.

5. The process of preparing polyhydrothiophenes containing a 3-acylamido substituent, which comprises reacting, with zinc and a lower aliphatic acid, a compound having the formula:

I CH

wherein R is acyl, R is a radical selected from the class which consists' gf alkyl, aryl and aralkyl radicals, and Q is a radical selected from the class which consists of oxitnino arylhydrazino and semicarbazido radicals,,Qsaid-reaction being carried out in the presence) acetic anhydrlde.

7. The process of preparing polyhydrothio- 'phenes, containing a 3-acetamido substituent which comprises reacting 2-(4'-carbomcth0xybutylidenei-3-isonitroso-4-benzamido tetrahydrothiophene with zinc, acetic acid and acetic anhydride.

8..-The process of preparing polyhydrothio; phenes containing a 3-acetamido substituent,-

which comprises reacting 2-(4-carbometho'xybutylidene) -3- (p-nitrophenylhydrazino) -4'-benz-.

amido-tetrahydrothiophene With-zinc, acetic :acid and acetic anhydride. 1 I I,

9. The process of preparing polyhydrothi'ophenes containing a 3-acylamido substituent, which comprises reacting 2-(4'-carboa1koxy-buty1idene)-3-isonitros0 4a-cylamid0-tetrahydro- 1o ingpoint of 162-163 C. I

1 thiophenes with zinc, a lower aliphatic acid and aiower aliphatic acid anhydride. 1 f

10. Arm esters of" 2-(4"-carboxy-buty1idene) 3:4-di(acy1amido) -tetrahydrothiophene.' I

11-. Araikyl esters I .of 2-(4'v-carboxy butyle idene) -3 :4-di(acy1a.mido') -tetrahydroth1ophene. 12'. D1-'2 (4"- car bomethoxy butylidene) -'3'- acetamido r 4 benzamido --tetrahydrothi0phene, having; when in substantially pure form, a melt-1 STANTONAnI-QRRIS.

."GLENEL'ARTHQ No references cited. 

